It is known that calcium carbonate may occur naturally or may be synthetically produced in three particular crystalline morphologies, calcite, aragonite, and less commonly found, vaterite. The vaterite form of calcium carbonate is metastable and irreversibly transforms into calcite and aragonite.
The calcite crystalline morphology is the most commonly used crystal form of calcium carbonate. Over 300 crystalline forms of calcite have been reported in the literature. Many of these crystal forms of calcite, such as scalenohedral, prismatic and rhombohedral, are readily available through precipitation production technology. Although less commonly known, an acicular crystalline form of calcite has also been reported. Acicular refers to the shape of the crystals, which are typically clusters of rod-shaped or needle-like crystalline morphologies . For example, acicular calcite morphology has been reported to occur in nature as pendent calcretes in semi-arid climates, Ducloux J. and Laouina, The Pendent Calcretes in Semi-Arid Climates, Catena, vol. 16, pages 237-249, (1989). Another acicular calcitic micromorphic form of calcium carbonate has been reported to occur in bauxite processing waste, Thomas T. L., Hossner L. R. and Wilding L. P., Micromorphology of Calcium Carbonate in Bauxite Processing Waste, Geoderma, vol. 48, pages 31-42, (1991).
It is also known that aragonitic calcium carbonate occurs naturally and may also be produced by precipitation production technology in acicular crystalline form. It is further known that acicular aragonite occurs predominately in rod-shaped or needle-shaped crystalline forms.
Although acicular calcite and acicular aragonite are known in the art as separate and distinct crystalline forms, compositions, having both acicular calcite and acicular aragonite in a state of co-existence, are unknown.
Therefore, what has been found to be novel and unanticipated by the prior art is a composition, method and use of calcium carbonate morphology having both acicular calcite and acicular aragonite crystalline form.